Plant for the reversible rolling of steel strip

ABSTRACT

A rolling plant has a reversible rolling mill with two stands. Each upright of the stands rests on a support structure via a bearing surface and is fastened thereto by a bolt or shank integral with the structure and cooperating with the upright via a removable fastening device. The bearing surface of each upright is provided on the lower face of the upright, without extending beyond the lateral faces directed along the rolling direction of the uprights, and is formed with a hole opening into a hollow housing provided in the upright and having an orifice opening onto a lateral face of the upright. The bolt or shank extends through the hole and projects into the housing, and the removable fastening device is placed inside the housing.

The invention relates to a rolling installation of the type comprising a two-stand reversing mill.

Steel strips may be rolled using different types of rolling installation. “Reversing” rolling installations make it possible to roll a strip, moving in a rolling direction, alternately in one direction and then the other. The strip is rolled by passing it through a mill comprising, between two coiling/uncoiling devices, one stand or two stands arranged successively in the rolling direction.

Two-stand reversing installations have a production capacity of 300,000 to 1,000,000 metric tons per year compared to a production capacity of 200,000 to 600,000 metric tons per year for “single stand” reversing installations. Two-stand reversing installations also have the advantage of reducing the number of rolling passes in one direction and then the other. Patent EP 0 618 018 B1 describes such a two-stand reversing rolling installation for cold rolling.

In the case of reversing rolling performed in more than three passes, the head and tail ends of the strip remain clamped to the mandrels of the coiling/uncoiling devices located on either side of the two stands. A service length between, firstly, the head or tail end of the strip and, secondly, the roll gaps in the stand located near to the coiling/uncoiling device to which is attached the head or tail end in question, is not rolled to the desired thickness.

Furthermore, at the end of the pass, an inter-stand length between the roll gaps of the two stands is not rolled to the required thickness. In fact, this inter-stand length has only been rolled by passing through one of the two stands, i.e. the stand located close to the coiling/uncoiling device to which is attached the head or tail end in question.

Thus, at each end of the strip, an end length corresponding to the sum of a service length and an inter-stand length has a thickness outside the tolerances. The two end lengths have to be removed after rolling, creating offcuts. Offcuts affect the performance of two-stand reversing installations.

For example, for a rolling mill using three passes to roll a steel coil with a width of up to 1600 mm, an initial thickness of 3 mm and a length of 700 m, to obtain a steel strip with a target thickness of 1 mm, a two-stand reversing rolling installation in which each stand has a rolling capacity of around 2,400 metric tons is required. To achieve this, each stand is for example fitted with backup rolls with a diameter of 1,250 mm and work rolls with a diameter of 450 mm. To withstand the corresponding stresses, each stand typically has uprights 9,000 mm tall and 4,000 mm wide. The center-to-center distance separating the planes of symmetry of the two stands, vertical planes in which the roll axes rest, is 6,000 mm.

In such installations the quantity of strip lost on the service lengths is 2% of the original coil. With a center-to-center distance between the two stands of 6,000 mm, the offcut corresponding to the two inter-stand lengths is 1% of the original coil. Consequently, the resulting total loss is greater than 3% of the original coil. This should be compared to the habitual loss of a single-stand mill which is around 2% and that of a continuous tandem mill which is negligible.

It should be noted that the center-to-center distance is necessarily greater than a minimum resulting from the geometry of the stands and their installation constraints on the building structure. In particular, according to the prior art, the uprights of the stands of the two-stand reversing mills include lugs in the building structure. A lug on an upright forms a protuberance, in the rolling direction, beyond the vertical plane of the face of the upright bearing the lug. In particular, the side face of an upright of the first stand, perpendicular to the rolling direction and oriented towards the second stand, has a lug projecting towards the second stand. Symmetrically, the side face of an upright of the second stand, perpendicular to the rolling direction and oriented towards the first stand, has a lug projecting towards the first stand. The lugs result in a center-to-center distance of 6,000 mm, or an inter-stand distance of 2,000 mm, the inter-stand distance corresponding to the distance separating the two external lateral faces located on each of the uprights of the first and second stands and facing one another.

The lugs have throughbores to accommodate elements to attach the uprights to the building structure. Moreover, the lower face of these lugs constitutes the support surface for the upright on the building structure. With regard to this, the lower face of the upright drops below the level of the lower faces of the lugs, and is situated above a pit created in the building structure, beneath the stand, to collect used lubricating oils.

We have attempted to reduce offcuts in two-stand reversing mills.

For example, the patent JP 03-138004 describes the use of extensions welded onto each end of the strip to be rolled, and a particular sequence for opening and closing the stands and the clamp to roll the entire strip to the required thickness.

Apart from the fact that this method takes a long time to implement, there is a risk of breaking around the junction between the extensions and the strip, in particular during rolling under traction.

The invention is therefore intended to reduce the length of the strip cut off during operation of a two-stand reversing rolling installation.

To achieve this the invention relates to a rolling installation of the type comprising a reversing mill with two stands, adjacent in a rolling direction, each stand having two roll supporting uprights, each upright resting on a support structure by means of a support surface and being fixed to the support structure by means of at least one shank attached to the support structure and cooperating with the upright by means of detachable fixing means. The support surface of each upright is provided on the lower face of the upright, without extending beyond the lateral faces of the uprights oriented in the rolling direction and includes at least one hole opening into a hollow seat provided for in the upright and having an aperture opening onto a lateral face of the upright. The shank attached to the support structure extends through the hole and projects into the seat, and the detachable fixing means is placed inside the seat.

According to the specific embodiments of the invention, the rolling installation has one or more of the following characteristics, separately or in any of the technically feasible combinations:

-   -   the hollow seat is a cell, the cell having an aperture opening         onto a lateral face of the upright, perpendicular to a direction         transversal to the rolling direction and oriented towards the         outside of the stand.     -   the hollow seat is a slot, the slot having an aperture opening         onto a lateral face of the upright, perpendicular to a direction         transversal to the rolling direction and oriented towards the         outside of the stand.     -   the detachable fixing means is a nut, the shank is a pin and the         support structure is solid concrete, the pin being anchored in         the solid concrete and inserted into the hole passing through         the upright of the stand and the nut being screwed to the pin.     -   the installation also includes means for driving the rolls         comprising a reduction gear including an input shaft intended to         be connected to a motor, first and second output shafts intended         to be connected to the rolls to be driven and at least one         intermediate shaft coupling the input shaft to the first and         second output shafts, and at least the axes of the output and         intermediate shafts are vertically superposed such as to reduce         the footprint in the rolling direction.     -   the installation also includes means to change rolls, including         a carriage shared by the first and second stands that can be         moved, in a direction perpendicular to the rolling direction,         between a service position near to the first and second stands         and a waiting position away from the first and second stands,         the carriage having at least two racks able to carry a train of         rolls and arranged side by side in the rolling direction, and         roll loading/unloading means enabling worn rolls to be unloaded         from a stand onto an empty rack and for new rolls to be loaded         from a rack into a stand.     -   the carriage includes a mobile deck that can be moved in         parallel to the rolling direction, and said at least two racks         are placed on the mobile deck.     -   the carriage includes four racks and the mobile deck can be         moved between the first and second positions, such that, in the         first position of the mobile deck, the racks of a first pair of         racks are respectively placed in the vertical plane of the rolls         of the first stand and the second stand, and, in the second         position of the mobile deck, the racks of a second pair of racks         are respectively placed in the vertical plane of the rolls of         the first stand and the second stand, the carriage having first         loading/unloading means to serve the first rack and second         loading/unloading means (324) to serve the second stand, it         being possible to load and/or unload the first and second stands         simultaneously or separately.     -   the installation is able to roll strips with an entry thickness         of up to 10 mm and up to 1,600 mm wide, and the distance between         the lateral face of an upright of the first stand, perpendicular         to the rolling direction and oriented towards the second stand,         and the lateral face of an upright of the second stand,         perpendicular to the rolling direction and oriented towards the         first stand, is less than 1,500 mm.     -   the distance between the lateral face of an upright of the first         stand, perpendicular to the rolling direction and oriented         towards the second stand, and the lateral face of an upright of         the second stand, perpendicular to the rolling direction and         oriented towards the first stand, is greater than the space         strictly necessary to enable an operator to pass through for         exceptional interventions, a space of at least 700 mm.

The invention and its advantages can be better understood from the description below, given purely by way of example, and drafted with reference to the attached drawings, in which:

FIG. 1 is a schematic representation of a two-stand reversing rolling installation;

FIG. 2 is a side view of a two-stand reversing rolling installation according to one embodiment of the invention;

FIG. 3 is a top view of the installation in FIG. 2;

FIG. 4 is a partial perspective view of the fixing means on the support structure of a stand of the installation in FIGS. 2 and 3;

FIG. 5 is a partial perspective view of an alternative embodiment of the fixing means of a stand on the support structure;

FIG. 6 is a front view of the reduction gears of the drive means of the rolls of the installation in FIGS. 2 and 3; and,

FIG. 7 is a front view of an alternative embodiment of the reduction gears of the drive means of the rolls.

FIG. 1 is a schematic representation of a two-stand reversing rolling installation 1 for rolling a metal strip M moving in a horizontal plane in a rolling direction A. The strip M is driven to move alternately in a positive direction (from left to right in FIG. 1) and in a negative direction (from right to left in FIG. 1). The rolling installation 1 includes, placed successively along the rolling direction A, a first stand 2 and a second stand 4. The first and second stands 2 and 4 are of the six-high type. Each stand 2, 4 is fitted with a pair of work rolls 6 and 7, a pair of intermediate rolls 8 and 9 and a pair of backup rolls 10 and 11. The axes of the different rolls of a stand rest in a single vertical plane P of symmetry of the stand.

The rolling installation 1 also includes, upstream of the first and second stands 2 and 4, a strip uncoiler 12, a first coiling/uncoiling device 14, a clamping device 16. The rolling installation 1 includes, downstream of the first and second stands 2 and 4, a deflector roll 18 and a second coiling/uncoiling device 20. The first and second coiling/uncoiling devices 14 and 20 are respectively provided with mandrels to apply traction to the strip M during rolling such as to increase the thickness reduction rate of the strip M.

The rolling installation 1 includes other elements, not shown but known to the person skilled in the art, such as a preparation device for the head end of the strip M, thickness measurement means, etc.

FIGS. 2 and 3 show the rolling installation 1 according to the invention in greater detail, in which the stand uprights are adapted to minimize the center-to-center distance between the two stands, the distance separating the planes of symmetry P of the first and second stands 2 and 4.

The first stand 2 includes two lateral uprights 22 arranged on either side of the rolling axis A in a transversal direction Y. The two lateral uprights 22 of the stand 2 are linked to each other in particular by upper crosspieces 24.

An upright 22 has an external shape contained within a rectangular parallelepiped. It has a rear face 26, perpendicular to the rolling direction A and oriented towards the second stand 4; a front face 27, perpendicular to the rolling direction A and oriented the opposite way to the rear face 26; a lower face 28, perpendicular to the vertical direction Z and oriented downwards; and an external lateral face 30, perpendicular to the transversal direction Y and oriented towards the outside of the stand. The upright 22 rests on a support structure 25, preferably made of concrete, by means of its lower face 28 comprising a flat support surface. The upright 22 is provided with an oblong window 32 in the vertical direction Z. The upright 22 is consequently ring-shaped. The window 32 is intended to receive the support means of the roll chocks 6 to 11.

The second stand 4 includes a pair of uprights 42 arranged on either side of the rolling direction A and connected to each other by upper crosspieces 44.

An upright 42 has a front face 46, perpendicular to the rolling direction A and oriented towards the first stand 2; a rear face 47, perpendicular to the rolling direction A and oriented the opposite way to the front face 46; a lower face 48, perpendicular to the vertical direction Z and oriented downwards, forming a support surface of the second upright 42 on the support structure 25; and it has an external lateral face 50 perpendicular to the transversal direction Y and oriented towards the outside of the second stand 4. One upright 42 is ring shaped, and defines internally a window 52 for the support means of the roll chocks 6 to 11.

Thus, the rear face 26 of the first stand 2 and the front face 46 of the second stand 4 are arranged opposite one another. The distance separating the front and rear faces 26 and 46 is the inter-stand distance D.

According to the invention, the inter-stand distance D is minimized by bringing the first and second stands 2 and 4 closer to one another in the rolling direction A. To enable this, the rear and front faces 26 and 46 do not have any projections, in the rolling direction A, forming a protuberance towards the other stand. The rear and front faces 26 and 46 are flat. As shown in detail in FIG. 2, an upright 22, 42 includes hollow seats intended to receive means for fixing the upright to the support structure 25.

In a first embodiment shown in FIG. 4, the upright 22 includes, in its lower part, a hollow seat forming a cell 62. This leads to the rear face 26 of the upright 22 and the external lateral face 30 of the upright 22. The upright 22 also has a throughbore 64, with a vertical axis opening, at one end, onto the lower face 28 of the upright 22 and, at the other end, onto the lower surface 66 of the cell 62.

The throughbore 64 enables the passage of a shank 80 of a pin, of which one end is anchored to the support structure 25 and the other end, threaded and free, protrudes out of the throughbore 64, inside the cell 62, above its lower surface 66. A nut 82 is screwed to the shank 80 and tightened against the lower surface 66 of the cell 62 to attach the upright 22 to the support structure 25. Thus, the cell 62 forms a seat to receive the nut 82.

The upright 22 also has a second cell 63 along the edge between its front face 27 and its external lateral face 30. A throughbore 65 leads to a cell 63 and enables the passage of a pin 80. A nut 82, seated in the cell 63, is screwed to the threaded end of the shank of the pin 80 and enables the fixing means of the upright 22 to be tightened to the support structure 25 at a second fixing point.

Similarly, an upright 42 of the second stand 4 has a first cell 72 opening onto the front face 46 and onto the external lateral face 50 of the upright 42, and a second cell 73 opening onto the rear face 47 and onto the external lateral face 50 of the upright 42. The throughbores 74 and 75 are arranged between the lower face 48 and the first and second cells 72 and 75 to enable the passage of pins 80. Nuts 82 are screwed to the threaded ends of the shanks 80 to attach the upright 42 to the support structure 25.

Thus, according to the invention, the fixing means of an upright to the support structure are within the footprint of the upright in the rolling direction A.

FIG. 5 shows a second embodiment of the hollow seats. The hollow seats of the lower part of an upright 122 is realized such as to form a horizontal slot 162 on the external lateral face 130 of the upright 122. The slot 162 extends from the front face 127 to the rear face 126 of the upright 122. A lower surface 166 of the slot 162 has three throughbores 163, 164 and 165 that lead to the lower surface 128 of the upright 122. They permit the passage of shanks with one end anchored to the support structure 25 and the other, threaded, end entering the slot 162. Nuts screwed to the threaded ends of the shanks are inserted into the slot 162. They enable, by tightening onto the lower face 166 of the slot 162, to fix the upright 122 to the support structure 25 at different fixing points.

To withstand the stresses applied to them, the person skilled in the art will be able to determine the geometry of the uprights as a function, among other things, of the shape of the cells, the position of the anchor points on the support structure, and the surface of the support face of the support structure actually making contact.

Although it is beneficial to minimize the inter-stand distance D to reduce the corresponding inter-stand length lost, a minimum space must be left between the rear and front faces 26 and 46 of the stands 22 and 24. Indeed, this space must be sufficient to enable the insertion and removal of tools such as the C-clamp of an X-ray thickness gauge used to measure the thickness of the strip in order to provide adjustment data to the control system of the rolling installation. Furthermore, albeit exceptionally, the possibility of a strip engagement problem in one of the stands or a breakage of the strip in the gap between the two stands occurring cannot be discounted. It is therefore necessary to retain an inter-stand distance to enable an operator to pass through. To assess the minimum dimension of the inter-stand distance, reference may be made to machine safety standards, and in particular standard EN 547 which proposes leaving a minimum space of 700 mm between two machines to enable access on all fours while enabling the body to move.

By way of example, and returning to the numerical data given in the introduction, the first and second six-high stands 2 and 4 have a rolling capacity of around 2,400 metric tons each. The backup rolls 10 and 11 have a diameter of 1,250 mm, the intermediate rolls 8 and 9, a diameter of 550 mm, and the work rolls 6 and 7, a diameter of 450 mm. Each stand 2, 4 typically has uprights 22, 24 9,000 mm tall and 4,000 mm wide. According to the invention the inter-stand distance D is reduced to 700 mm. Consequently, the center-to-center distance is reduced by 1,300 mm and the inter-stand length of the strip M is 4,700 mm. For a production of 1,000,000 metric tons per year, the annual gain realized by implementing this invention could reach 1,000 metric tons of strip.

In the installation according to the invention, the drive means of the work, intermediate or backup rolls, depending on the installation type, have a reduced footprint in the rolling direction A.

As shown in FIG. 3 and FIG. 6, in a first embodiment, the drive means of the rolling installation have two reduction gears 200 arranged one after the other, parallel to the rolling direction A, on the drive side of the first and second stands 2 and 4.

The reduction gear 200 includes: an input shaft 212, coupled to a drive motor 214, and two output shafts 216 and 218, coupled respectively to each of the rolls to be driven. Where appropriate, a pair of extensions 220 couples the output shafts 116 and 118 and the rolls to be driven. The reduction gear 200 also includes, between the input shaft 212 and the output shafts 216 and 218, at least one intermediate shaft 222 bearing a set of cogs meshed with cogs either on the output shafts 216 and 218, or the input shaft 212.

In this first embodiment, the axes of the output shafts 216 and 218 and intermediate shaft 222 are arranged horizontally one above the other in a vertical plane, while the axis of the input shaft 212 is arranged laterally in relation to the axis of the intermediate shaft 222. The reduction gear 200 has an “L” layout.

A second embodiment of the reduction gear in the installation according to the invention is shown schematically in FIG. 7. According to this second embodiment, all of the axes of the shafts of the reduction gear 210 are arranged horizontally one above the other, in a vertical plane. The reduction gear 210 is vertical and has a reduced footprint in the rolling direction A.

In the installation according to the invention, the roll change system has a single carriage 300 as shown in FIGS. 2 and 3. The carriage 300 is fitted with wheels 302 and can be moved along the rails 304, arranged in the transversal direction Y. The carriage 300 is moved by actuating the movement means 306 between a waiting position away from the first and second stands 2 and 4, and a service position near to the first and second stands 2 and 4. FIG. 3 shows the carriage 300 in its waiting position away from the first and second stands 2 and 4.

The carriage 300 has a mobile deck 310 fitted with a row of four racks 312 a-d arranged side by side in the rolling direction A. The racks 312 a and 312 b serve the first stand 2 and the racks 312 c serve the second stand 4. Each rack 312 a-d is able to carry a train of rolls comprising the work rolls 6 and 7 and the backup rolls 8 and 9. At the beginning of the roll change method, the two racks 312 a and 312 c carry a train of new rolls, fitted with their chocks, while the other two racks 312 b and 312 d are empty, waiting to load the used rolls removed from each of the first and second stands 2 and 4.

The mobile deck 310 is moveable by translation in the rolling direction A, along the rails 316 provided on the carriage 300. The mobile deck 310 is moved in relation to the carriage 300 by actuating means such as a rack (not shown) on the carriage 300.

In the first position of the deck 310, the vertical plane of symmetry of the racks 312 b and 312 d coincides with the plane of symmetry respectively of the first and second stands 2 and 4. The first and second push/pull devices 322 and 324, provided on the carriage 300, can pull the used rolls from the first and second stand 2 and 4 to place them on the racks 312 b and 312 d.

In the second position of the mobile deck 310, the vertical planes of symmetry of the racks 312 a and 312 c coincide with the planes of symmetry respectively of the first and second stands 2 and 4. The first and second push/pull devices 322 and 324 can then be actuated to push the new rolls, waiting in racks 312 a and 312 c, into each of the first and second stands 2 and 4.

Once the rolls have been replaced, the carriage 300 is moved to its waiting position away from the mill.

In a synchronous roll-change method, the first and second push/pull devices 322 and 324 are actuated simultaneously to pull out the used rolls and push in the new rolls. This ensures a quick roll change.

Alternatively, an asynchronous roll-change method is possible in which the push/pull devices 322 and 324 are actuated separately in order to enable the rolls of one of the stands of the mill to be changed.

The person skilled in the art will be able to modify the installation described above to implement other roll replacement methods. Thus, in certain types of installation, the drive is provided via the backup or intermediate rolls. The work rolls are then driven by friction on the intermediate rolls. In this type of installation the drive side of the mill is relatively unencumbered. A roll loading/unloading carriage may therefore be provided on the drive side of the mill. Furthermore, although a push/pull roll change system has been described, alternatively, the roll change system may be push-through only or pull-through only. 

1-10. (canceled)
 11. A rolling installation with a reversing mill, comprising: two stands disposed adjacent one another in a rolling direction of the rolling installation, each stand including two uprights for supporting a plurality of rolls; a support structure carrying said uprights, with each said upright resting on a support surface of said support structure; wherein said support surface of each said upright is provided on an internal face thereof, without projecting beyond a lateral face of said upright in a rolling direction; said upright having a hollow seat formed therein with an aperture opening onto the lateral face of said upright, and at least one through hole opening into said hollow seat; at least one shank fixing each said upright to said support structure, said shank being attached to said support structure, extending through said bore, and projecting into said hollow seat, and a detachable fixing device disposed in said hollow seat and cooperating with said upright to affix said upright to said support structure.
 12. The installation according to claim 11, wherein said hollow seat is a cell, said cell being formed with an aperture opening onto a lateral face of said upright, perpendicular to a direction transverse to the rolling direction and oriented towards an outside of the respective said stand.
 13. The installation according to claim 11, wherein said hollow seat is a slot, said slot being formed with an aperture opening onto a lateral face of said upright, perpendicular to a direction transverse to the rolling direction and oriented towards an outside of the respective said stand.
 14. The installation according to claim 11, wherein said detachable fixing device is a nut, said shank is a threaded bolt, said support structure is formed of solid concrete and said bolt is anchored in said solid concrete, and said bolt projects through said through hole in said upright of said stand and said nut is screwed onto said bolt.
 15. The installation according to claim 11, which further comprises means for driving the rolls, including a reduction gear having an input shaft to be connected to a motor, first and second output shafts to be connected to the rolls to be driven, and at least one intermediate shaft coupling said input shaft to first and second output shafts, and wherein at least the axes of said output shafts and intermediate shafts are vertically superposed to thereby reduce a footprint in the rolling direction.
 16. The installation according to claim 11, which further comprises means to change rolls, including a carriage shared by said first and second stands and movable, in a direction perpendicular to the rolling direction, between a service position in a vicinity of said first and second stands and a waiting position away from said first and second stands, said carriage having at least two racks configured to carry a train of rolls and arranged side by side in the rolling direction, and a device for roll loading and roll unloading configured to unload worn rolls from a stand onto an empty rack and to load new rolls from a rack into a stand.
 17. The installation according to claim 16, wherein said carriage includes a mobile deck capable of movement in parallel to the rolling direction, and wherein said at least two racks are placed on said mobile deck.
 18. The installation according to claim 17, wherein said at least two racks of said carriage are four racks and said mobile deck is movable between the first and second positions, such that, in the first position of said mobile deck, the racks of a first pair of racks are respectively placed in a vertical plane of the rolls of said first stand and said second stand, and, in the second position of said mobile deck, the racks of a second pair of racks are respectively placed in the vertical plane of the rolls of said first stand and said second stand, said carriage having first loading/unloading means configured to serve the first stand and second loading/unloading means configured to serve the second stand, enabling the first and second stands to be loaded and/or unloaded simultaneously or separately.
 19. The installation according to claim 11, configured to roll strips with an entry thickness of up to 10 mm and a width of up to 1,600 mm, and wherein a distance between said lateral face of an upright of the first stand, perpendicular to the rolling direction and oriented towards the second stand, and said lateral face of an upright of the second stand, perpendicular to the rolling direction and oriented towards the first stand, is less than 1,500 mm.
 20. The installation according to claim 19, wherein the distance between said lateral face of an upright of the first stand, perpendicular to the rolling direction and oriented towards the second stand, and said lateral face of an upright of the second stand, perpendicular to the rolling direction and oriented towards the first stand, is greater than a space strictly necessary to enable an operator to pass for an exceptional intervention.
 21. The installation according to claim 20, wherein the space strictly necessary to enable an operator to pass is measured at least 700 mm. 